[FFmpeg-devel] [PATCH 1/2] avdevice/decklink_dec: use a custom memory allocator

[Dave Rice]

> On Jun 4, 2018, at 4:21 PM, Marton Balint <cus at passwd.hu> wrote:
> 
> The default memory allocator is limited in the max number of frames available,
> and therefore caused frame drops if the frames were not freed fast enough.

I’ve been testing this patchset today. Yesterday I was occasionally getting “Decklink input buffer overrun!” errors with this command:

/usr/local/opt/ffmpegdecklink/bin/ffmpeg-dl -v info -nostdin -nostats -t 1980 -f decklink -draw_bars 0 -audio_input embedded -video_input sdi -format_code ntsc -channels 8 -raw_format yuv422p10 -i "UltraStudio Express" -metadata:s:v:0 encoder="FFV1 version 3" -color_primaries smpte170m -color_trc bt709 -colorspace smpte170m -color_range mpeg -metadata creation_time=now -f_strict unofficial -c:v ffv1 -level 3 -g 1 -slices 16 -slicecrc 1 -c:a pcm_s24le -filter_complex "[0:v:0]setfield=bff,setsar=40/27,setdar=4/3; [0:a:0]pan=stereo| c0=c0 | c1=c1[stereo1];[0:a:0]pan=stereo| c0=c2 | c1=c3[stereo2]" -map "[stereo1]" -map "[stereo2]" -f matroska output.mkv -an -f framemd5 output.framemd5

With the patchset applied, I haven’t had that buffer overrun error re-occur. 

> Signed-off-by: Marton Balint <cus at passwd.hu>
> ---
> libavdevice/decklink_dec.cpp | 50 ++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 50 insertions(+)
> 
> diff --git a/libavdevice/decklink_dec.cpp b/libavdevice/decklink_dec.cpp
> index 510637676c..897fca1003 100644
> --- a/libavdevice/decklink_dec.cpp
> +++ b/libavdevice/decklink_dec.cpp
> @@ -21,6 +21,9 @@
>  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
>  */
> 
> +#include <atomic>
> +using std::atomic;
> +
> /* Include internal.h first to avoid conflict between winsock.h (used by
>  * DeckLink headers) and winsock2.h (used by libavformat) in MSVC++ builds */
> extern "C" {
> @@ -98,6 +101,44 @@ static VANCLineNumber vanc_line_numbers[] = {
>     {bmdModeUnknown, 0, -1, -1, -1}
> };
> 
> +class decklink_allocator : public IDeckLinkMemoryAllocator
> +{
> +public:
> +        decklink_allocator(): _refs(1) { }
> +        virtual ~decklink_allocator() { }
> +
> +        // IDeckLinkMemoryAllocator methods
> +        virtual HRESULT STDMETHODCALLTYPE AllocateBuffer(unsigned int bufferSize, void* *allocatedBuffer)
> +        {
> +            void *buf = av_malloc(bufferSize + AV_INPUT_BUFFER_PADDING_SIZE);
> +            if (!buf)
> +                return E_OUTOFMEMORY;
> +            *allocatedBuffer = buf;
> +            return S_OK;
> +        }
> +        virtual HRESULT STDMETHODCALLTYPE ReleaseBuffer(void* buffer)
> +        {
> +            av_free(buffer);
> +            return S_OK;
> +        }
> +        virtual HRESULT STDMETHODCALLTYPE Commit() { return S_OK; }
> +        virtual HRESULT STDMETHODCALLTYPE Decommit() { return S_OK; }
> +
> +        // IUnknown methods
> +        virtual HRESULT STDMETHODCALLTYPE QueryInterface(REFIID iid, LPVOID *ppv) { return E_NOINTERFACE; }
> +        virtual ULONG   STDMETHODCALLTYPE AddRef(void) { return ++_refs; }
> +        virtual ULONG   STDMETHODCALLTYPE Release(void)
> +        {
> +            int ret = --_refs;
> +            if (!ret)
> +                delete this;
> +            return ret;
> +        }
> +
> +private:
> +        std::atomic<int>  _refs;
> +};
> +
> extern "C" {
> static void decklink_object_free(void *opaque, uint8_t *data)
> {
> @@ -924,6 +965,7 @@ av_cold int ff_decklink_read_header(AVFormatContext *avctx)
> {
>     struct decklink_cctx *cctx = (struct decklink_cctx *)avctx->priv_data;
>     struct decklink_ctx *ctx;
> +    class decklink_allocator *allocator;
>     AVStream *st;
>     HRESULT result;
>     char fname[1024];
> @@ -1017,6 +1059,14 @@ av_cold int ff_decklink_read_header(AVFormatContext *avctx)
>     ctx->input_callback = new decklink_input_callback(avctx);
>     ctx->dli->SetCallback(ctx->input_callback);
> 
> +    allocator = new decklink_allocator();
> +    ret = (ctx->dli->SetVideoInputFrameMemoryAllocator(allocator) == S_OK ? 0 : AVERROR_EXTERNAL);
> +    allocator->Release();
> +    if (ret < 0) {
> +        av_log(avctx, AV_LOG_ERROR, "Cannot set custom memory allocator\n");
> +        goto error;
> +    }
> +
>     if (mode_num == 0 && !cctx->format_code) {
>         if (decklink_autodetect(cctx) < 0) {
>             av_log(avctx, AV_LOG_ERROR, "Cannot Autodetect input stream or No signal\n");
> -- 
> 2.16.3
> 
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